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GIS in midas' installations


Discussion

Instrumentation
Midas was founded in April 1994 by a few alumni of Indian Institute of Technology, Madras, with the aim of developing a technology that could reduce the cost and maintenance of telecommunication connectivity. With this in mind, Midas developed the corDECT Wireless Local Loop (WLL) technology that reduced the connectivity cost and maintenance. This system, as described by Purohit, is expected to provide a superior alternative to the buried cable method.

Wallset


 Wallset IP

PLATE 3

Multi Wallset

PLATE 3
The corDECT system (Plate 1) consists of a DECT Interface Unit (DIU), a Compact Base Station (CBS), Wallset (WS), a Base Station Distributor (BSD) and a Network Management System (NMS). The DIU performs system control and does the interfacing to telecom network. The DIU acts as a mini exchange. The Compact Base Station offers wireless access in the area on twelve simultaneous channels and the Wallset is a wireless fixed terminal connected to any standard telephone, modem or a fax machine. The Wallset Internet Protocol (WS-IP) provides simultaneous voice and data facility to the subscriber(s). The Base Station Distributor (BSD) connects four remotely-located CBSs to the DIU, using E1 link, while the Network Management System (NMS) manages multiple DIUs and their associated CBS and Wallsets. Each DIU can provide connections to 1000 subscribers and would need about 20 Base stations and 1000 Wallsets along with their other accessories.

The DIU (Plate 2) is a DECT (Digital Enhanced Cordless Telecommunication) exchange for wireless subscribers and provides an interface to Public Switched Telephone Network (PSTN). The DIU handles functions such as call processing, CBS powering and PCM/ADPCM (Pulse Code Modulation/Adaptive Differential PCM) transcoding. System Operation and Maintenance (O&M) and remote fault monitoring can be performed from the DIU or alternatively from a remote location using the Network Management System (NMS).

Base Station Station Distributor

PLATE 5
The Compact Base Station (Plate 3) is a small wall mounted or pole mounted (over a hill or otherwise) unit. Each unit serves one cell, providing upto 12 simultaneous speech channels. A CBS has two antennae for diversity. A directional antenna, with significant gain, can be used when coverage required is either confined to certain directions or coverage area is divided into sectors covered by different base stations. Otherwise an Omni-directional antenna can be used. A CBS can provide a distance of 10 kilometres for communication. In some instances, a Relay Base Station (RBS) is used to enhance the range of communication for the corDECT system by another 25 kilometres.

The Wallset (Plate 4) is a small wall-mounted unit, with an external antenna and powered from A/C mains. An internal battery provides backup in case of power failure. The external antenna provides gain and extends the range of a CBS in areas where CBS density is low. The Wallset provides a standard RJ-11 telephone socket so that any telephone, fax machine, modem or even a payphone can be connected to it. A multi-wallset is used to support four standard phones, a payphone and modem or fax machine. A Wallset-Internet Protocol (WS-IP) will provide Internet access at 35/70 kbps, with simultaneous voice and data. This connects to a PC serial port, without the need for a modem. Th WS-IP can be upto 10 kilometres away from the CBS.

The Base Station Distributor (Plate 5) is an optional unit and will be used if a cluster of CBS is to be located at a distance of about 100 kilometres from the DIU. The BSD is connected to the DIU on E1 lines and each E1 line feeds to the 4 CBSs. The BSD is locally powered by -48V source and also feeds power to the CBS.

The Network Management System (NMS) is software and is used to manage upto 30 DIUs and their subscribers. The NMS is interfaced to the PSTN on an E1 link (2MB - PCM link) and could be located anywhere. The NMS performs operation & maintenance (O & M) functions for all the DIUs and the subscribers connected to them. It monitors the health of every card on each of the DIUs as well as all the CBSs. The NMS carries out subscriber management for all subscribers. When the DIUs are configured as an independent exchange, the NMS also provides billing to all the subscribers.

Thus the corDECT Wireless Local Loop technology is a versatile and efficient system of communication which can offer connectivity to the entire India at a very low cost and maintenance. No digging for copper wire laying will be necessary. The test installations of the system is shown in plate 6.

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